help me with a new crankset

i need to get a new crank for my fixie, but i don't really know what to look for. All i really know is that i want a chain ring with 42 teeth, and probably 170 mm.
so far i've found THIS and THIS. Do either of those look any better, and can i really expect to get a decent crankset for 20 or 30 bucks? And also, what does BCD mean?

Eww, biopace, I know Sheldon likes 'em but I'd still be scared to run a biopace ring.

As for your question, you could spend a bit extra and get an IRO crankset. They're very nice, and go for about $80 which isn't bad for a brand new crankset. Although, they only come with a 46T chainring. BCD refers to the spacing between the holes on the chainring, Bolt Circle Diameter.

chucks bikes has a set of sugino AC130 170mm cranks for friggin 15 bucks. They're nice (crazy nice for 15 bucks), I just got them. Sans chain ring though, if you can find one and have the short stack chainring bolts to boot, you've got yourself a nice crank set for cheap.

i have to say that my sugino 75's were completely worth the money. one of those 'you get what you pay for' dealies. honestly, made my ride 100% better than the bulletproof ones I had before, or the deore (ouch) ones before that.

You are right on the money so far dude. Those Ultegra cranks would be perfect(although the Biopace kinda scares me, just fear of the unknown though). I just picked up a set of 600's for a friends buiid off of eBay for $40 last week. I like to use Shimano because I find that most Shimano cranks mate very well with a 107mm UN-53 BB to get the chainline in pretty tight. It takes the guesswork out of the whole chainline process. Keep shooting for a set like those and you will get a nice crankset for cheap.